Poly(etherimide-siloxane) copolymers (also known as polysiloxane/polyimide block copolymers) have been explored as coatings for electrical wires due to their flame resistant properties and high temperature stability. These copolymers are attractive for applications of this type because the polyetherimide blocks impart desirable properties such as high temperature resistance, high strength, good wear resistance, good flame retardant properties, and low smoke density. The polysiloxane blocks contribute flexibility, good low-temperature properties, and temperature stability.
Aromatic polyketones such as polyaryletherketones are crystalline polymers valued due to their resistance to high temperatures, crystallizability, melt extrudability, and injection moldability, thereby making them versatile and useful in many applications. Crystallization of polymers is an important feature in polymer processing, because the structure developed during crystallization can affect the mechanical and physical properties of the polymer product. The crystallization of polymers under processing conditions is essential for optimizing the processing conditions to obtain a product with desired properties. Aromatic polyketones, such as polyaryletherketones frequently suffer from brittleness, e.g., poor toughness (low ductility), making them unsuitable for many applications.
There has been a long felt need to develop a composition that has high impact strength and low flexural modulus and high tensile elongation, specifically one that has a ductility exceeding that of aromatic polyketones yet retains the advantageous processing features. Polyaryletherketone blends have sought to solve this problem, but these blends have suffered from drawbacks such as insufficient ductility, delamination and the like.
Accordingly, there remains a need in the art for improved thermoplastic compositions having the desired combination of physical properties including low flammability, high temperature stability, low flexural modulus, high tensile elongation, high impact strength, and improved tear strength. Thermoplastic compositions having this combination of properties can be useful for applications including electrical wire coatings.